Jonathan Barratt, PhD, FRCP: The kidney biopsy in IgA nephropathy is not only the only way we can diagnose this disease, but it also provides incredibly valuable prognostic information. It has 2 functions in terms of helping the patient give the diagnosis but also as Jerry has mentioned, working with other clinical variables allow us to give important prognostic information to the patient.

Gerald B. Appel, MD: I would say that any biopsy can give you value in certain ways; diagnosis, prognosis, and a guide to therapy, those 3 things and of course here diagnostically it's crucial. I don't think you can call anything IgA nephropathy unless you've had the biopsy. Prognostically, we think this is very important because on all the new prognostic models that go through this, the MEST score is there. They haven't necessarily hit it on the C, but you can hit on the C if you want in terms of that. Then in terms of therapy, thinking about which pathway is involved, how important the complement pathway is and even whether you're going to use non-specific therapy. I always say the bottom line for patients is, is it going to change what you do then it makes it very important because then you can always justify the biopsy.

Jonathan Barratt, PhD, FRCP: As Jerry mentioned he's seeing a patient with IgA nephropathy almost every time he opens the clinic door. In terms of kidney biopsies, what proportion of your workload every week would you say is an IgA nephropathy diagnosis?

Sanjeev Sethi, MD: Again, extremely common, we have a very large volume with the Mayo Clinic of course but I would say I would see an IgA every day. Sometimes I see 4 biopsies a day of IgA nephropathy. What's very interesting from the pathologist standpoint, exactly as the clinician, extremely variable, you can see an IgA nephropathy and the biopsy looks pristine and clean and normal except for the IgA on the immunofluorescence microscopy. On the other end you can see IgA neuropathy with bright IG on the IF and 9 out of 10 glomeruli are globally sclerosed. Even though sclerosed glomeruli hold chunks of IgA.

Jonathan Barratt, PhD, FRCP: That's what fascinates me. You're looking at the IgA immunofluorescence on a kidney biopsy. It does not tell you how active that disease is. You can have gloms that are full of IgA with very little activity and gloms full of IgA that are very inflamed.

Sanjeev Sethi, MD: Absolutely.

Jonathan Barratt, PhD, FRCP: There's something more subtle about IgA nephropathy than simply IgA immune complexes deposited in the kidney. We've talked about a very common disease, and we've talked about something that you see a lot and a relatively straightforward approach to the biopsy.

Transcript Edited for Clarity